Supersensitized light-sensitive silver halide photographic emulsion

ABSTRACT

THE EMULSION CONTAINS AT LEAST ONE COMPOUN OF THE FORMULA   S=C&lt;(-N(-R1)-CO-C(=P)-X-)   WHEREIN P IS   1-R2-PYRID-2(1H)-YLIDENE OR 1-R3-PYRID-4(1H)-YLIDENE   R2 AND R3 ARE INDIVIDUALLY AN ALKYL GROUP; X IS S, O, N, OR N-R WHEREIN R IS HYDROGEN, AN ALKYL GROUP OR A LOWER ALKYL GROUP; AND R1 IS AN ALKYL, ALLYL OR ARYL GROUP IN COMBINATION WITH AT LEAST ONE COMPOUND OF THE FORMULA   1-R5,2-(S=),3-R6,4-(O=),5-(3-R4,Z1,Z2-BENZOXAZOL-2(3H)-   YLIDENE)=CH-CH=)IMIDAZOLIDINE   WHERE R4 IS AN ALKYL GROUP; R5 AND R6 ARE INDIVIDUALLY AN ALKYL OR ARYL GROUP; AND Z1 AND Z2 ARE INDIVIDUALLY A HYDROGEN OR HALOGEN ATOM OR AN ALKYL, ALKOXY OR ARYL GROUP, SAID Z1 AND Z2 MAY LINK TO EACH OTHER TO FORM A BENZENE RING. THE EMULSION WHEN SUBJECTED TO SUPERSENSITIZATION DISPLAYS IDEAL COLOR SENSITIVITY.

United States Patent Claims priority, application Japan, Jan. 16, 1970, 45/3 820 rm. (:1. dose 1/08 US. Cl. 96-122 Claims ABSTRACT OF THE DISCLOSURE The emulsion contains at least one compound of the formula P=C-X wherein P is Ra R:

R and R are individually an alkyl group; X is S, 0, N, or N-R wherein R is hydrogen, an alkyl group or a lower alkyl group; and R is an alkyl, allyl or aryl group, in combination with at least one compound of the formula wherein R is an alkyl group; R and R are individually an alkyl or. aryl group; and Z and Z arevindividually a hydrogen or halogen atom or an alkyl, alkoxy or aryl group, saidZ and Z may link to each other to form a benzene ring. The emulsion when subjected to supersensitization displays ideal color sensitivity.

wherein P is Patented Nov. 21, 1972 where R and R are individually an alkyl group; Q is a non-metallic atomic group necessary for forming a 5-membered ring; and R is an alkyl, allyl or aryl group, in combination with at least one compound of the general formula wherein R, is an alkyl group; R and R are individually an alkyl or aryl group; and Z and Z are individually a hydrogen or halogen atom or an alkyl, alkoxy or aryl group, said 2, and Z may link each other to form a benzene ring.

As is well known, the inherent light-sensitive wavelength region of a silver halide emulsion is ordinarily an extremely limited short wavelength region (400 mp. or less) of ultraviolet ray or blue light. It is well known that as a means for the spectral sensitization of such silver halide emulsion, the use of certain cyanine dye is markedly efiective. It is also well known that when a combination of the above-mentioned sensitizing dye and a certain other sensitizing dye or an organic cornpound is added to a silver halide emulsion, light sensitivity greater than that recognized as the sum of the sensitizing effects of the individual compounds can be imparted to the emulsion. Such eifect is called as supersensitization, and many combinations of compounds have already been reported.

In applying such supersensitization method to a silver halide emulsion, particularly a lith-type silver chlorobromide emulsion, it is desirable that not only the increase in color sensitization effect is attained but also such conditions as set forth below are satisfied.

(l) The supersensitization method does not disturb the characteristics of the lith-type emulsion which has an extremely high contrast.

(2) The supersensitization method should contribute to the improvement in fine dot quality of a half-tone image without deteriorating the sharpness thereof,

(3) The supersensitization method should not bring about any dye stain or fog on the film after high contrast development.

Further, it is desirable that in the case of a lith-type silver chlorobromide emulsion which requires a visible wavelength region, particularly a blue lightor green lightsensitive region, the supersensitization shows high sensitivity in the blue light-sensitive region without desensitizing the inherent sensitivity thereof and provides sharp and good dots by development within such a relatively short period of time as 2 to 3 minutes.

However, most of the conventional supersensitization methods and chiefly employed for the treatment of ordinary silver iodobromide emulsions for negatives, and the actual state is such that neither of said methods can satisfy the aforesaid conditions when applied to high contrast silver chlorobromide emulsions.

An object of the present invention is to provide a lightsensitive silver halide photographic material which has been subjected to supersensitization capable of satisfying the aforesaid conditions.

Another object of the invention is to provide a lightsensitive silver halide photographic material which has no detrimental interactions with co-existing photograpihc additives and which maintains stabilized photographic properties even when stored for a long period of time.

As the result of extensive studies, we have found that when a combination of at leastone compound of the General Formula I and at least one compound of the General Formula II is incorporated into a silver halide photographic emulsion, not only a marked increase in color sensitization effect can be attained but also all the aforesaid conditions can be satisfied.

Both of the compounds represented by the General Formulas I and II are merocyanine type sensitizing dyes, and when these sensitizing dyes are used in combination according to the present invention, spectral sensitivity maximum values exhibited by the individual sensitizing dyes can be brought to a unified collective maximum value to make it possible to attain the best ortho-sensitivity. That is due to synergistic effect derived from the specific combination of said compounds, the purple light region and green light region of emulsion are markedly enhanced in sensitization. Further, the combination of said compounds has such characteristic that when the compounds are added to a lith-type emulsion, to which is applieda 20 lith developer containing hydroquinone as a principal ingredient together with aldehyde, it is possible to obtain a sharp dot image which is high in contrast.

Typical examples of the compounds of the General Formulas 1 and II are enumerated below, but compounds usable in the present invention are not limited only to these.

Typical examples of the compounds of the General Formula I are as follows:

i =G-0 N O=C-N Exemplified Compound No. R; R

(17) CH; C1H5 (18) CH; CH;

CHCH;OH CH CH10COC;H CH1CH;SO3K

/ i /O=S O=C-III m I Hi N l R:

Exemplified Compound No. R: R

(22) -C:H5 C:H5

(23) CH| Q (24) CH| CH2CH2OCOCH| (25) --CH| -CH1CH1SO3K r C-N N 1 /C=S o=o-Iri: 1

Exemplified' Compound No. R; R R

Q (28) Q CHCOOH C-N\ I /(3:3 O=CI l i I N in Exemplified Compound No. R; R R

( CHI Q C:Ha

(30) -C2Hs C:Hs C: 5

5 6 Typical examples of the'compounds of the General (37) Formula H are as follows: im

' /C=CH-OH=CN\ s1 moo 0:8 N l I 7 O: -N 0 EMSOaH 1 \C=CHCH=C--N\ l /C=S 10 0=CN 2H5 at (38) 0 7 H oniooon C=GHCH=CN 7 Q i V 01- c=s 0 N (1H s01: 0=C N C=CH-CH=O. N 2): a

\ CHzCOOH C=CH--CH=CN I I o=s V N 0 (ornsox: 0:0-N 33 2 A a v 3, 1

C=CH-CH=CN\ L c=s mcmcoon (40) I 2 2 C=OH-CH=C-I!I\ Q 0:5 (34) O on on OH N a enrol-1100011 o= N onmsoma (41) on on on N (3H CH coon 0:0.N

2 (35) cmcoon a omcmom C=CH QH=(] N A light-sensitive photographic material, which has been subjected to supersensitization by incorporation of a spe- N cific combination of the above-mentioned compounds,

a SO'K (bi-N has such excellent characteristics as mentloned previously,

and can display ideal color sensitivity. Thus, the combination of said compounds imparts quite excellent properties not only to a lith-type light-sensitive material but also to a light-sensitive photographic material comprising other silver chloride or silver chlorobromide emulsion. The distribution in sensitization maximum wavelength (36) 0 of a silver halide emulsion according to the present in- H1O CHlCOOH vention is variable depending on the kinds and proportions c=cH- cH=0 N of the sensitizing dyes of the general Formulas I and II.

The sensitizing dyes may be added in the form of a solu- N tion in a water-miscible organic solvent such as methanol (132E! or ethanol. Alternatively, each of the sensitizing dyes may may be added individually in the form of a solution in such organic solvent as mentioned above. The time of addition of said sensitizing dyes to a silver halide emulsion may be any stage during preparation of the emulsion, but

t a is preferably after completion of the second ripening, in 7 1 r general. The amounts of the sensitizing dyes to be added vary depending on the kind of the silver halide emulsion used. Ordinarily, however, the total amount of the sensitizing dyes of the General Formulas I and II is variable in a wide range of 1 mg. to 200 mg. per kg. of the silver halide emulsion. In this case, the mixing ratio of the sensitizing dye of the General Formula I to the sensitizing dye of the General Formula II is preferably 1:10 to :1 by weight.

Silver halide emulsions usable in the present invention include silver chloride, silver chlorobromide and silver bromide emulsions. These emulsions may have been incorpated with such sensitizers as noble metal and sulfur sensitizers, or with polyalkylene oxide type compounds as contrast-improving agents. Further, the emulsions may have been optically sensitized over the whole visible light regions by additional incorporation of other sensitizing dyes, e.g. carbocyanine dyes. Particularly when red light sensitivity is desired to be attained, the use of thiacarbocyanine dyes is preferable. The emulsions may further contain ordinary photographic additives such as stabilizers, hardeners, coating aids, etc.

The above-mentioned silver halide photographic emulsions containing the compounds are individually coated on a suitable support such as glass, cellulose triacetate base, polyester base or paper, and then dried, whereby the light-sensitive silver halide photographic materials of the present invention can be obtained.

The present invention is illustrated in further detail below with reference to examples, but the examples are illustrative and the invention is, of course, not limited to these.

EXAMPLE 1 A lith-type silver chlorobromide emulsion containing 2.0 mol percent of silver bromide which had been treated with a gelatin coagulant was subjected to second ripening according to gold sensitization method and then divided into several portions. Each divided emulsion was incorporated with methanol solutions of the exemplified compounds shown in Table 1, either singly or in combination of two. Subsequently, the emulsion was allowed to stand at about 40 C. for minutes to stabilize sensitiveness, added with a suitable amount of a polyalkylene oxide derivative as a tone-hardening agent and further with a hardening agent and a coating aid, coated on a film base and then dried to prepare green-sensitive lith-type lightsensitive materials.

For comparison, a control sample was prepared in the same manner as above, except that the two sensitizing dyes (a) and (b) shown below which are disclosed in US. Pat. 2,977,229 were used in combination.

Control dyes These samples were individually exposed to a light of 125 lux (2,660 K.) through blue and green filters having transmission maximums at 450 mg and 525 m respectively, using sensitometer Model KS-VII (manufactured by Konishiroku Photo Industry Co., Ltd.), and then developed at 20 C. for 3 minutes with a developer of the following composition:

8 Hot water ml 500 Addition product of formaldehyde and sodium Water to make 1,000 ml.

The results obtained were as shown in Table 1. In the table, the relative speed is a value calculated by regarding as 1-00 the green light speed of the sample using the control dyes (a) and (b), and the dye stain is a density value I measured by use of a complementary color filter.

TABLE 1 Rela- Relative tive Resid- Amounts of exemplified purple green ual color Sample compounds added light light (dye No. (mg/kg. emulsion) speed speed stain) Control dyes, (a) 30 mg. -i- 60 100 0. 03

(b) 30 mg. (l) 50 mg 60 0. 02 (34) 50 60 0.03 4 (1) 30mg. (34) 30 mg" 150 0.02 (9) 5 100 50 0.02 (35) g 4O 80 0. 02 (9) 30 mg. (35) 30111 170 0.02 90 60 0.02 (37) 50 mg 50 85 0.03 10 (19) 30 mg. (37) 30 mg 110 0.02

As is clear from Table 1 and the drawings shown later, the samples incorporated with combinations of the compounds according to the present invention are more excellent in sensitization degree in individual sensitizing region than the samples incorporated with individual compounds, and are greater in speed and less in formation of dye stain than the control sample.

In the accompanying drawings, FIG. 1 shows a spectral sensitivity courve of a silver chlorobromide emulsion; FIG. 2 shows spectral sensitivity curves of the sample 2 (dotted line) and of the sample 3 (solid line); and FIG. 3 shows a spectral sensitivity curve of the sample 4 according to the present invention.

EXAMPLE 2 Example 1 was repeated, except that the divided emulsions were individually incorporated with each of such combinations of the exemplified compounds as shown in Table 2, to prepare green-sensitive lith-type light-sensitive photographic materials. The sensitometry of each sample was effected in the same manner as in Example 1 to calculate the relative speed thereof, and the contrast was expressed in terms of an average gradient between the point where the density was 0.5 and the point where the density was 2.0. The evaluation of dots was carried out in such a manner that the sample was brought into close contact with a contact screen exposed and then subjected to development under the same conditions as in the case of the sensitometry, and the resulting dots were visually investigated by means of a microscope. The evaluation of dots was represented by each of the ratings 1 to 5, assuming that the rating of dots which were free from fringes and highest in sharpness was 5, and the rating of dots which were extremely large in amount of fringes was 1. The control dyes used in this example were the same as in Example 1.

TABLE 2 Rela- Relative tlve Amounts of exemplified purple green Evalu- Sample compounds added light light 0011- ation No. (mg/kg. emulsion) speed speed trast of dots 11 Control dyes (a) 30 mg. 60 100 8.0 2-3 l2 (4) 30 mg. (32) 30 mg.-... 180 230 ll 3 l3 (4) 30 mg. (35) 30 mg 100 15 5 14 (ll) 30 mg. (38) 30 mg..." 220 12 4 15 (11) 30 mg. (34) 30 mg 190 200 12 4 16 (22) 30 mg. (39) 30 mg 200 240 11 3 17 (22) 30 mg. (41) 30 mg 13 4 As is clear from Table 2, the samples 12 to 17 according to the present invention showed markedly excellent characteristics as compared with the control sample in every respect of speed, contrast and dot quality.

EXAMPLE 3 A silver chlorobromide emulsion containing 20 mol percent of silver bromide was subjected to second ripening and then divided into several portions, which were then individually incorporated with each of such combinations of exemplified compounds as shown in Table 3. Subsequently, the emulsions were sensitized in the red light region by addition of such amount as shown in Table 3 of a 1:1 mixture of anhydro-3,3-' -sulfopropyl-9-ethyl- 4,5,4',5'-dibenzothiacarbocyanine hydroxide (hereinafter referred to as Red 1) and 3-'y-sulfopropyl-9-ethyl-4,5- dibenzo-3', 8-sulfobutyl-5'-methylthiacarbocyanine sodium salt (hereinafter referred to as Red 2), and sufficiently stabilized in optical sensitization. Subsequently, the same additives as in Example 1 were added to prepare panchromatically sensitized lith-type light-sensitive materials.

The sensitometry of the thus prepared samples was carried out in such a manner that the samples were exposed to light through the blue and green filters used in Example 1 and a red filter capable of transmitting a ight of more than 600 mg in wavelength, and then developed at 20 C. for 3 minutes with D-ll developer formulated by Eastman Kodak Co. The results obtained were as shown in Table 3. In the table, the relative speed is a value calculated by assuming as 100 the speed of a sample containing only the red-sensitive dye Red 1.

TABLE 3 Rela- Rela- Relative tlve tlve Amount of exemplified purple green red Sample compounds added light light light No. (mg/kg. emulsion) speed speed speed Fog 18 Control sample containing 100 100 100 0. 08

only red-sensitive dye (Red 1) 20 mg. 19 (5) 20 mg. (33) 20 mg. 280 190 105 0. 08

led 1) 20 mg. (Red 2) mg. 20 (14) 20 mg. (31) 20 mg. 220 160 110 0. 09

(Red 1) 20 mg. (Red 2) 20 mg. 21 (26) 20 mg. (38) 20 mg. 170 130 .1 100 0.08

(Red 1) 20 mg. (Red 2) 20 mg.

wherein P is t t R: R2

R and R are individuallyan alkyl group; X is S, O, N or NR wherein R is hydrogen, an aryl group or a lower alkyl group; and R is an alkyl, allyl 0r aryl group, in combination with at least one compound of the General Formula II,

I o-s HaCH CH:

and

3. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein the compound of the Gen- 1 12 eral Formula II is one member selected from the group 4. The light-sensitive silver halide photographic emulconsisting of: sion as claimed in claim 1, wherein the total amount of o the compound of the General Formula I and that of the (31m General Formula II is within the range of 1 mg. to 200 C=CH-CH=C-N 5 mg. per kilogram of said emulsion. 5. The light-sensitive silver halide photographic emul- N sion as claimed in claim 1, wherein said emulsion is of the O=C-N HzCHzCOOH hth-type.

References Cited UNITED STATES PATENTS 2,972,539 2/1961 Jones 96-122 2,977,229 3/1961 Jones 96-126 FOREIGN PATENTS l 918,308 9/1954 Germany 96-422 0: N (gmhsolm J. TRAVIS BROWN, Primary Examiner US. Cl. X.R.

and

0 CHICOOH O=CHCH=CN 

